Examine source code of simple-adj-tab-switcher

{
  "manifest_version": 2,
  "name": "simple-adj-tab-switcher",
  "version": "1.0.0",
  "description": "switch to adjacent tabs with shortcut",
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_title": "simple-adj-tab-switcher"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "@simple-adj-tab-switcher",
      "strict_min_version": "58.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "commands": {
    "next-tab": {
      "suggested_key": {
        "default": "Alt+Shift+Right"
      },
      "description": "next tab"
    },
    "prev-tab": {
      "suggested_key": {
        "default": "Alt+Shift+Left"
      },
      "description": "previous tab"
    }
  }
}